This relates generally to manufacturing techniques for electronic devices, and more particularly, to methods for forming assemblies using adhesive.
Adhesives are widely used in manufacturing. For example, electronic devices often include housings and structures that are attached to each other with pressure sensitive adhesive. In some situations it is difficult to use pressure sensitive adhesive to attach structures to each other. For example, if two parts must slide past each other during assembly, it may be necessary to attach the parts to each other using liquid adhesive rather than a layer of pressure sensitive adhesive. The liquid adhesive can flow during the assembly process and will not cause the two parts to bind to each other prematurely, whereas a layer of pressure sensitive adhesive might cause the two parts to become stuck before they have reached their proper positions.
A variety of liquid adhesives are available. Some glues cure chemically. For example, two-part epoxies and methyl methacrylate (MMA) adhesives cure upon mixing resin with hardener. Cyanoacrylate (CA) adhesive is activated by exposure to moisture. Other glues are cured by application of elevated temperatures. Curing mechanisms such as these often produce undesirable outgassing and can be difficult to control.
Satisfactory control and minimal outgassing can be achieved by using adhesives that are cured by application of ultraviolet (UV) light. For example, ultraviolet-light-cured (UV) epoxy can be used to attach metal and plastic parts in an electronic device. In a typical manufacturing process, uncured UV epoxy is applied to structures that are to be attached to each other. Once the structures are in their desired positions, UV light from a UV lamp is applied to the UV epoxy. This cures the UV epoxy.
In some product designs, it is awkward or impossible to expose the UV epoxy using a UV lamp. For example, if the UV epoxy is located in an interior portion of an assembly, walls or other parts of the assembly will block light from the UV lamp.
To allow UV epoxy to be used to assemble parts where the UV epoxy is located in the interior of the assembly, holes are formed in the parts. During manufacturing, a technician can insert a UV light wand into the interior portion of the assembly through the holes. The internal application of UV light using a UV wand requires the use of holes in the assembly that are large enough to accommodate the UV wand. The holes may be unsightly and may reduce the ability of the assembly to withstand environmental exposure to dust and moisture.
It would therefore be desirable to be able to provide improved techniques for assembling structures using light-sensitive adhesives.